(CNN) -- Emergency crews early Sunday sifted through the wreckage left behind by a wave of tornadoes that swept across Iowa before midnight.
One of the twisters caused enough damage to prompt Iowa Gov. Terry E. Branstad to issue a disaster proclamation in Monona County, according to a statement released by the governor's office.
The proclamation allows officials to use state funds to help.
Authorities said the extent of the damage is unclear because the twister struck at night. Stefanie Bond, a public information officer for the state's Homeland Security & Emergency Management Division, said the National Guard is in Mapleton. Bond also said that natural gas service has temporarily been shut off in the city.
Amateur video recorded by storm chasers shows a large funnel cloud spinning across a flat terrain outside Mapleton.
In the background, a passenger can be heard exclaiming, "It's going to hit that town! ... Mapleton's in big trouble!" READ MORE AT CNN.COM